Method for preparing aqueous emulsions

ABSTRACT

Aqueous emulsions for impregnating organic fibers, comprising, in addition to water and dispersants, (1) a diorganopolysiloxane having a Si-bonded hydroxyl group in each terminal unit and whose organic radicals are free of basic nitrogen atoms; (2) an organopolysiloxane containing diorganosiloxane units in which the two organic radicals are monovalent hydrocarbon radicals and also contains at least two monovalent SiC-bonded organic radicals per molecule having a basic nitrogen atom in which the organopolysiloxane is present in the emulsion in an amount of from 5 to 50 weight percent based on the weight of the diorganopolysiloxane (1); (3) an organosilicon compound selected from an organosilane containing at least two SiOC-bonded monovalent organic radicals consisting of carbon, hydrogen and possibly oxygen and/or partial hydrolyzates thereof, in which the organosilicon compound is present in the emulsion in an amount of from 2 to 6 weight percent based on the total weight of the diorganopolysiloxane (1) and organopolysiloxane (2); and (4) a condensation catalyst, which is present in an amount of from 0.2 to 1 weight percent based on the total weight of the diorganopolysiloxane (1) and organopolysiloxane (2). 
     These aqueous emulsions are prepared by mixing the organosilicon compound (3) with an emulsion of diorganopolysiloxane (1) and organopolysiloxane (2) and thereafter mixing the resultant mixture with the condensation catalyst (4).

The present invention relates to aqueous emulsions and more particularlyto a method for preparing aqueous emulsions having better stability.

BACKGROUND OF THE INVENTION

Aqueous emulsions of organopolysiloxanes have been applied to organicfibers to improve their resistance to shrinkage and to impart a durablesoft handle. U.S. Pat. No. 3,876,459 to Burrill, for example, disclosestreating wool with an aqueous emulsion containing (A) adiorganopolysiloxane having a Si-bonded hydroxyl group in each terminalunit and whose organic radicals are free of basic nitrogen; (B) anorganosilane containing an organic radical which contains a basicnitrogen atom or a partial hydrolyzate of such organosilane or thereaction product of component (A) with such organosilane or partialhydrolyzate thereof; and possibly (C) a silane containing 3 or 4SiOC-bonded alkyl or alkoxyalkylene radicals as well as; (D) acondensation catalyst. Koerner et al, however, disclose in U.S. Pat. No.4,137,179 that such emulsions are unstable.

Therefore, it is an object of the present invention to provide stableaqueous emulsions. Another object of the present invention is to providestable aqueous emulsions which may be applied to fibers. Still anotherobject of the present invention is to provide stable aqueous emulsionswhich impart a pleasant hand and high resilience to fibers. A furtherobject of the present invention is to provide treated fibers which willhave a pleasant hand and high resilience after repeated cleanings inwater or organic solvents. A still further object of the presentinvention is to provide a method for preparing stable aqueous emulsionswhich may be applied to fibers.

SUMMARY OF THE INVENTION

The foregoing objects and others which will become apparent from thefollowing description are accomplished in accordance with thisinvention, generally speaking, by providing a method for preparingaqueous emulsions for impregnating organic fibers which comprises mixing(1) a diorganopolysiloxane containing a Si-bonded hydroxyl group in eachterminal unit and whose organic radicals are free of basic nitrogenatoms; and (2) an organopolysiloxane which contains diorganosiloxaneunits in which the organic radicals are monovalent hydrocarbon radicalsand at least two monovalent SiC-bonded organic radicals per moleculewhich contain a basic nitrogen atom with water and dispersant to form anaqueous emulsion; mixing (3) an organosilicon compound selected from anorganosilane containing at least two SiOC-bonded monovalent organicradicals consisting of carbon, hydrogen and possibly oxygen and/or apartial hydrolyzate of such a silane with the aqueous emulsion and thenadding to the resultant emulsion, (4) a condensation catalyst, in whichcomponent (2) is present in the emulsion in an amount of from 5 to 50weight percent based on the weight of component (1); component (3) ispresent in the emulsion in an amount of from 2 to 6 weight percent basedon the total weight of components (1) and (2) and component (4) ispresent in the emulsion in an amount of from 0.2 to 1 weight percentbased on the total weight of components (1) and (2).

DESCRIPTION OF THE INVENTION

Diorganopolysiloxanes (1) containing a Si-bonded hydroxyl group in eachterminal unit and whose organic radicals are free of basic nitrogenatoms which have been or could have been used heretofore in thepreparation of aqueous emulsions for impregnating organic or inorganicfibers may be used in the method of this invention. The preferreddiorganopolysiloxanes are those represented by the following generalformula:

    HOSiR.sub.2 O(SiR.sub.2 O).sub.n H,

where R represents the same or different monovalent hydrocarbon radicalsand n is an integer having a value such that the average viscosity ofthese diorganopolysiloxanes (1) is from 500 to 50,000 mPa.s at 25° C.The hydrocarbon radicals represented by R preferably have from 1 to 20carbon atoms per radical. Examples of hydrocarbon radicals which can bepresent in the diorganosiloxane units of diorganopolysiloxane (1) arealkyl radicals such as methyl, ethyl, n-propyl and isopropyl as well asbutyl, octyl, tetradecyl and octadecyl radicals; aliphatic radicalswhich contain aliphatic multiple bonds such as vinyl, allyl and hexenylradicals; cycloaliphatic hydrocarbon radicals such as cyclopentyl andcyclohexyl radicals; aromatic hydrocarbon radicals such as the phenyland naphthyl radicals; alkaryl radicals such as the tolyl radical andaralkyl radicals such as the benzyl radical. It is preferred that atleast 80 percent of the number of hydrocarbon radicals in thediorganopolysiloxane (1) be methyl radicals because of theiravailability.

Although only one type of diorganopolysiloxane (1) need be used, it ishowever possible to use a mixture of at least two different types ofdiorganopolysiloxanes (1).

The diorganopolysiloxane (1) can be prepared either by a polymerizationwhich takes place at least essentially in the absence of water or it canbe prepared by a polymerization in an aqueous emulsion.

The viscosity of diorganopolysiloxane (1) preferably ranges from about2000 to 10,000 mPa.s at 25° C.

Organopolysiloxane (2) contains at least two monovalent SiC-bondedorganic radicals per molecule having a basic nitrogen atom anddiorganosiloxane units, in which the two organic radicals arehydrocarbon radicals. The diorganosiloxane units, in which the twoorganic radicals are hydrocarbon radicals, may be represented by thegeneral formula:

    R.sub.2 SiO

where R is the same as above. The examples of hydrocarbon radicals whichmay be present in diorganopolysiloxane (1) also applies equally toexamples of hydrocarbon radicals which may be present inorganopolysiloxane (2).

The siloxane units which contain SiC-bonded organic radicals having abasic nitrogen atom which are present in organopolysiloxane (2),preferably have the following general formula:

    R.sup.2.sub.2 NR.sup.1 R.sub.b (R.sup.3 O).sub.a SiO.sub.(3-a-b)/2'

where R is the same as above; R¹ represents a divalent hydrocarbonradical; R² is hydrogen or the same or different alkyl or aminoalkylradical; R³ is the same or different alkyl radical having from 1 to 4carbon atoms; a is 0, 1 or 2; b is 0, 1 or 2 and the sum of a+b is atmost 2.

Examples of divalent hydrocarbon radicals represented by R¹ aremethylene, ethylene, propylene, butylene, cyclohexylene, octadecylene,phenylene and butenylene. The n-butylene radical is preferred due to itsavailability.

The examples of the alkyl radicals represented by R also apply equallyto the alkyl radicals represented by R².

Examples of aminoalkyl radicals represented by R² are those having thefollowing formulas:

H₂ N(CH₂)₃ --

H₂ N(CH₂)₂ NH(CH₂)₃ --

H₂ N(CH₂)₂ --

(H₃ C)₂ N(CH₂)₂ --

H₂ N(CH₂)₅ --

H(NHCH₂ CH₂)₃₋₋ and

C₄ H₉ NHCH₂ CH₂ NHCH₂ CH₂₋₋.

Preferably at least one R² is hydrogen.

Examples of alkyl radicals represented by R³ are in particular methyl,ethyl and ispropyl radicals.

The organopolysiloxanes (2) used in the method of this inventionpreferably have a viscosity of from 20 to 20,000 mPa.s at 25° C.

One type of organopolysiloxane (2) can be used; however, it is alsopossible to use a mixture of at least two different types oforganopolysiloxanes (2).

Organosilicon compounds (3) which contain at least two SiOC-bondedmonovalent organic radicals consisting of carbon, hydrogen and possibleoxygen preferably have the following general formula:

    R.sup.4.sub.a Si[(OCH.sub.2 CR.sup.5 H).sub.m OX].sub.4-a,

where R⁴ represents an alkyl radical substituted by at least one aminoor imino group, such as the examples described above for aminoalkylradicals R² or R⁴ is the same as R; R⁵ is hydrogen or an alkyl radicalhaving from 1 to 4 carbon atoms; X is hydrogen or an alkyl radicalhaving from 1 to 4 carbon atcms or an acyl radical having from 1 to 5carbon atoms, preferably three carbon atoms or less; a is 0, 1 or 2 andm is 0 or an integer having a value of 1 to 30, provided that m is atleast 1 when X is hydrogen or an acyl radical.

Examples of organosilicon compounds are organosilanes or partialhydrolyzates thereof, such as methyltrimethoxysilane,methyltriethoxysilane, the ethoxypolysiloxane, often referred to as"ethylsilicate 40" and which contains 40 weight percent SiO₂ and silaneshaving the following formulas:

H₂ N(CH₂)₂ HN(CH₂)₃ Si(OCH₃)₃

CH₃ Si(OCH₂ CH₂ OCH₃)₃

CH₃ O(CH₂ CH₂ O)₆ (CH₂)₃ Si(OCH₃)₃

H₂ N(CH₂)₂ NH(CH₂)₃ Si(OCH₃)₂.

One type of organosilicon compound (3) can be used; however, it is alsopossible to use a mixture of at least two different types of such asilanes or partial hydrolyzates thereof.

Any catalyst which has has been or could have been used heretofore inthe condensation of Si-bonded condensable groups can be used as thecondensation catalyst (4) in this invention. Examples of such catalystsare in particular the tin or zinc salts of carboxylic acids in which thehydrocarbon radicals can be bonded directly to the tin atom. Specificexamples of such tin compounds are di-n-butyltin dilaurate, tinoctoates, di-2-ethylhexyltin dilaurate, di-n-butyltin di-2-ethylhexoate,di-2-ethylhexyltin di-2-ethylhexoate and zinc octoates. Other examplesof condensation catalysts (4) are alkoxy titanates such as butyltitanates and triethanolamine titanates and zirconium compounds.

One type of catalyst (4) can be used or a mixture of at least twodifferent types of condensation catalysts (4), may be employed in thisinvention. An example of a mixture of condensation catalysts which maybe employed are di-n-butyltin dilaurate and triethanolamine titanate.

The relative proportions of the components employed in the aqueousemulsions are critical in order to obtain a stable emulsion. Theorganopolysiloxane (2) having a basic nitrogen atom per molecule shouldbe present in the emulsion in an amount of from 5 to 50 weight percentbased on the weight of the diorganopolysiloxane (1) and the amount oforganosilicon compound (3) ranges from 2 to 6 weight percent based onthe total weight of diorganopolysiloxane (1) and organopolysiloxane (2).The condensation catalyst (4) is present in the emulsion in an amount offrom 0.2 to 1 percent based on the total weight of diorganopolysiloxane(1) and organopolysiloxane (2).

When the organopolysiloxane (2), organosilicon compound (3) andcondensation catalyst (4) are employed in the emulsions in amounts belowthe limits prescribed above, fibers impregnated with these emulsions donot have as pleasant a hand or as high a resilience as fibersimpregnated with emulsions containing organopolysiloxane (2),organosilicon compound (3) and condensation catalyst (4) within theprescribed limits; even though these properties are retained by thefibers after repeated cleaning with water or organic solvent. Whenorganosilicon compound (3) and condensation catalyst (4) are employed inthe emulsions in an amount which exceeds the limits described above, theresultant emulsions are unstable. In addition, the use of more than 50weight percent of organopolysiloxane (2), based on the weight ofdiorganopolysiloxane (1) is uneconomical since no additional advantagesare obtained over those obtained using lower amounts.

Any dispersant which has been used or could have been used heretofore toproduce aqueous emulsions of organopolysiloxanes for impregnatingorganic fibers may be used as dispersants in this invention.

Preferred dispersants are nonionic emulsifiers such as the polyglycolethers of alkanols or phenol or alkylphenols such as nonylphenolpolyglycol ethers, tert-butylphenol polyglycol ethers, polyoxyethylenesorbitan hexastearate, polyoxyethylene isotridecyl ethers andtrimethylnonylethers of polyethylene glycol which contain 6 to 14ethylene oxide units per molecule; polyoxyethylene sorbitan oleatehaving a saponification number of 102 to 108 and a hydroxyl number of 25to 35 and dimethylpolysiloxane-ethylene oxide block copolymers.

Other examples of dispersants which can be used in the method of thisinvention are anionic emulsifiers such as alkylbenzenesulfonates andsodium alkylarylpolyethyleneglycol sulfonates.

Other examples of dispersants which can be used in the method of thisinvention are cationic emulsifiers such as tetraalkylammonium chlorides.

The dispersants are preferably used in an amount of from 3 to 20 weightpercent and more preferably from 5 to 10 weight percent, based on thetotal weight of diorganopolysiloxanes (1), organopolysiloxane (2),organosilicon compound (3) and condensation catalyst (4).

The emulsions prepared in accordance with this invention preferablycontain from 35 to 80 weight percent and more preferably from 45 to 60weight percent of water, based on the total weight of the emulsion. Whenthe emulsion contains a lower content of the substances other thanwater, the resultant emulsion may be unstable. A higher content ofsubstances other than water, generally produces emulsions which can behandled only with difficulty because of their higher viscosity.

When the emulsions prepared in accordance with this invention areapplied to organic fibers, they are preferably diluted to a content offrom about 95 to 99.5 weight percent of water, based on the total weightof the emulsion.

These emulsions may be prepared in any high-speed stirring apparatuswhich has been used or could have been used heretofore in preparingaqueous emulsions.

In preparing the aqueous emulsions, organosilicon compound (3) is firstmixed with an aqueous emulsion of diorganopolysiloxane (1) andorganopolysiloxane (2), followed by the addition of the condensationcatalyst (4). Diorganopolysiloxane (1) and organopolysiloxane (2) can beemulsified separately or together in water. Preferably, organosiliconcompound (3) is dissolved or emulsified in water before it is mixed withan aqueous emulsion of diorganopolysiloxane (1) and organopolysiloxane(2). Likewise, the condensation catalyst (4) is preferably dissolved ordispersed in water before it is mixed with an aqueous mixture consistingof diorganopolysiloxane (1), organopolysiloxane (2) and organosiliconcompound (3).

Other substances, such as textile finishing agents may also be includedin the emulsions of this invention. Examples of such substances areso-called "crease-resistant finishes" such asdimethyloldihydroxyethyleneurea (DMDHEU) mixed with zinc nitrate,particularly when the fibers to be impregnated are made of cellulose orcotton or are fiber mixtures which contain cellulose or cotton fiber.Because of emulsion stability reasons, blending of the emulsions of thisinvention with other substances should be done only immediately beforeimpregnating fibers with these blends.

Emulsions prepared in accordance with this invention are stable at roomtemperature for at least 6 months. They crosslink to form an elastcmericfilm upon removal of water. The film produced from a freshly preparedemulsion does not essentially differ from the film produced from anemulsion stored at room temperature for 6 months.

All organic fibers in the form of thread, yarn, non-wovens, mats, weavesor knit textiles which heretofore could be impregnated withorganosilicon compounds from an aqueous emulsion can be impregnated withthe emulsions prepared in accordance with this invention. The fibers canbe natural or synthetic in origin. Examples of fibers which can beimpregnated with the emulsions prepared in accordance with thisinvention are fibers made of keratin, particularly wool, cotton, rayon,hemp, natural silk, polypropylene, polyethylene, polyester,polyurethane, polyamide, cellulose acetate and mixtures of at least twosuch fibers. The textiles can be present in the form of fabric webs orarticles of clothing or parts of articles of clothing.

With keratin and particularly wool, shrinkage by felting can beprevented by impregnating keratin with the emulsion prepared inaccordance with this invention, especially when the keratin has beenpretreated with clorine, rinsed and neutralized.

An emulsion prepared in accordance with this invention can be applied tofibers in any manner which is known for impregnating organic fibers withliquid substances, for example, by immersion, coating, pouring,spraying, rolling on, pressing, knife or doctor coating or padding.

The crosslinkable organopolysiloxane is crosslinked on the fibers afterthe evaporation of the water. This evaporation is preferably carried outat a temperature of from 50° to 180° C.

The weight gain of fibers impregnated with the emulsions prepared inaccordance with this invention after evaporation of the water ispreferably from 0.1 to 20 weight percent and more preferably from 0.5 to3 weight percent, based on the weight of the individual fibers prior toimpregnation.

In the following examples, all parts and percentages are by weightunless otherwise specified.

A high-speed stirrer was used in the apparatus to prepare the emulsionsin each of the following examples.

EXAMPLE 1

(a) About 35 parts of a dimethylpolysiloxane which has a Si-bondedhydroxyl group in each terminal unit and a viscosity of 6000 mPa.s at25° C. are first mixed with 4 parts of a nonylphenol polyglycol etherwhich is obtained by reacting nonylphenol (1 mol) with ethylene oxide(15 mol) and then with 4 parts water.

An emulsion is prepared from the mixture thus obtained by the additionof 57 parts water.

(b) The procedure described in (a) above is repeated except that 35parts of the product obtained from the reaction of adimethylpolysiloxane having a Si-bonded hydroxyl group in each terminalunit and a viscosity of 100 mPa.s at 25° C. and a silane having thefollowing formula:

    H.sub.2 N(CH.sub.2).sub.2 NH(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3

is substituted for the 35 parts of the dimethylpolysiloxane with aSi-bonded hydroxyl group in each terminal unit. This reaction producthas an amine number (number of ml of 1N HCl required to neutralize 1 g)of 1.2 and a viscosity of 65 mPa.s at 25° C.

(c) About 25 parts di-2-ethylhexyltin dilaurate are first mixed with 3parts tert-butylphenol polyglycol ether which is obtained by reactingtert-butylphenol (1 mol) with ethylene oxide (13 mol) and 3 parts water.An emulsion is prepared from the mixture thus obtained by adding 69parts water.

(d) About 90 parts of the emulsion whose preparation is described in (a)above are mixed with 4.5 parts of the emulsion whose preparation isdescribed in (b) above. About 5 parts of a solution which is obtained byadding 40 parts of a silane having the following formula

    CH.sub.3 Si(OCH.sub.2 CH.sub.2 OCH.sub.3).sub.3

to 60 parts water is added to the aqueous emulsion consisting of theemulsions (a) and (b) above. About 0.5 parts of the emulsion whosepreparation is described in (c) above are mixed into the mixture thusobtained.

The emulsion thus obtained is stable even after storage for 6 months ina closed container at 40° C.

A polyester knit is immersed in an aqueous emulsion prepared by mixing30 parts of the emulsion prepared in (d) above with 970 parts by volumeof water. The polyester is squeezed out to a 100 percent liquid uptakeand then heated at 150° C. for 10 minutes. The polyester thus obtainedhas a soft, pleasant and elastic hand which is still present even after5 washings at 30° C. in a household washing machine or after treatingfive times for 20 minutes with perchloroethylene.

EXAMPLE 2

(a) About 30 parts of an 80 percent solution of zirconium octoate inwhite spirit (zirconium content: 18 percent) are first mixed with 3parts of the tert-butylphenol polyglycol ether described in Example 1(c)above and 3 parts of water. An emulsion is prepared from the mixturethus obtained by the addition of 64 parts of water.

(b) About 85 parts of an emulsion prepared in accordance with Example1(a) above are mixed with 10 parts of an emulsion prepared in accordancewith Example 1(b) above. About 4 parts of a solution prepared by adding40 parts of a silane having the following formula

    H.sub.2 N(CH.sub.2).sub.2 NH(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3

to 60 parts water are added to the aqueous emulsion.

About 1 part of the emulsion prepared in (a) above is mixed into theresultant mixture.

The emulsion thus obtained is stable even after storage for 6 months ina closed container at 40° C.

EXAMPLE 3

(a) The procedure described in Example 1(a) is repeated except that 35parts of the product obtained from the reaction of adimethylpolysiloxane having a Si-bonded hydroxyl group in each terminalunit and a viscosity of 100 mPa.s at 25° C. with a silane having thefollowing formula

    H.sub.2 N(CH.sub.2).sub.2 NH(CH.sub.2).sub.3 (CH.sub.3)Si(OCH.sub.3).sub.2

are substituted for the 35 parts of dimethylpolysiloxane having aSi-bonded hydroxyl group in each terminal unit. This reaction producthas an amine number of 0.1 and a viscosity of 5000 mPa.s at 25° C.

(b) About 50 parts of the emulsion prepared in accordance with Example1(a) above are mixed with 10 parts of the emulsion prepared in (a)above. About 4 parts of a solution prepared by adding 40 parts of asilane having the following formula

    CH.sub.3 Si(OCH.sub.2 CH.sub.2 OCH.sub.3).sub.3

to 60 parts water is added to the resultant aqueous emulsion.

About 1 part of the emulsion prepared in Example 2(a) above is mixedinto the resultant mixture.

The emulsion thus obtained is stable even after storage for 6 months ina closed container at 40° C.

A 100 percent cotton fabric is immersed in an aqueous emulsion which isprepared by mixing 40 parts of an emulsion prepared in accordance with(b) above with 100 parts of a 45 percent aqueous solution ofdimethyloldihydroxyethyleneurea, 20 parts of zinc nitrate and 860 partsof water. The fabric is then squeezed out to a 100 percent liquid uptakeand finally heated at 150° C. for 10 minutes. The fabric treated in thismanner has a soft, pleasant and elastic hand which is still present evenafter 5 washings at 30° C. in a household washing machine or aftertreating with perchloroethylene five times for 20 minutes as in chemicalcleaning.

What is claimed is:
 1. An aqueous emulsion for impregnating organicfibers comprising in addition to water and a dispersant: (1) adiorganopolysiloxane having a Si-bonded hydroxyl group in each terminalunit, in which the organic radicals of the diorganopolysiloxane are freeof basic nitrogen atoms; (2) an organopolysiloxane containingdiorganosiloxane units in which the organic radicals of thediorganosiloxane are monovalent hydrocarbon radicals, and at least twomonovalent SiC-bonded organic radicals per molecule having a basicnitrogen atom, in which the organopolysiloxane (2) is present in theemulsion in an amount of from 5 to 50 weight percent based on the weightof diorganopolysiloxane (1); (3) an organosilicon compound selected fromthe group consisting of an organosilane containing at least twoSiOC-bonded monovalent organic radicals containing carbon and hydrogenor carbon, hydrogen and oxygen, partial hydrolyzates of suchorganosilane and mixtures thereof, in which the organosilicon compound(3) is present in the emulsion in an amount of from 2 to 6 weightpercent based on the total weight of the diorganopolysiloxane (1) andorganopolysiloxane (2); and (4) a condensation catalyst, which ispresent in the emulsion in an amount of from 0.2 to 1 weight percentbased on the toatal weight of the diorganopolysiloxane (1) andorganosiloxane (2), in which the emulsion is prepared by mixing theorganosilicon compound (3) with an aqueous emulsion containingdiorganopolysiloxane (1) and organopolysiloxane (2) and thereaftermixing the resultant emulsion with the condensation catalyst.
 2. Theemulsion prepared by the method of claim 1, wherein the organosiliconcompound (3) is mixed with water before it is mixed with an aqueousemulsion of diorganopolysiloxane (1) and organopolysiloxane (2).
 3. Theemulsion prepared by the method of claim 1, wherein the condensationcatalyst (4) is mixed with water before it is mixed with an aqueousemulsion containing diorganopolysiloxane (1), organopolysiloxane (2) andorganosilicon compound (3).